Sphere lapping apparatus



Nov. 19, 1963 H. E. G. ARNESON SPHERE LAPPING APPARATUS 4 Sheets-Sheet 1Filed Aug. 10, 1961 INVENTOR. #42010 I. 6'. HIM E504! Nov. 19, 1963 H.E. G. ARNESQN SPHERE LAPPING APPARATUS 4 Sheets-Sheet 2 Filed Aug. 10,1961 INVENTOR. M42040 6 flRA/Esa Nov. 19, 1963 H. E. G. ARNESON3,110,987

SPHERE LAPPING APPARATUS Filed Aug. 10, 1961 4 Sheets-Sheet 3 I N VENTOR. #42040 if 6 flRn/Esa/v BY JQM 4 TTORIVEVS Nov. 19, 1963 H. E. 5.ARNESON 3,110,987

SPHERE LAPPING APPARATUS Filed Aug. 10. 1961 4 Sheets-Sheet 4 FIE. '7

INVENTOR. #4200 E 6. 192M550 WM M 3,110,987 SPHERE LAPPING APPARATUSHarold E. G. Arneson, Professional Instruments Co., 6824 W. Lake St,Minneapolis, Minn. Filed Aug. 10, 1961, Ser. No. 130,537 12 Claims. (Cl.51-417) This invention relates to an improvement in grinding andpolishing apparatus, and particularly in such apparatus as is used inconnection with the grinding and polishing of spherical bodies and whichis more specifically referred to as lapping apparatus.

In a lapping apparatus it is desirable to have perfect random movementof the work piece and this is developed as a result of the relativefriction of the laps or lap heads. However in presently designed lappingapparatus there is present the element of the pressure of gravity inaddition to the pressure of the lap heads. The pressure of gravityprevents a uniformity of 'lappin g pressure over the surface of the workpiece. As a result of the lack of uniformity in lapping pressure theredevelops a systematic motion which tends to prevent perfect randommotion on the part of the work piece and to directly affect the degreeof sphericity resulting from the lapping.

It is desirable therefore to construct and arrange the lapping apparatusto offset or negative the tendency for gravity pressure to develop or bepresent. It is desirable to support the lapping members or lappingassembly so that the lap heads will be unaifected by gravity in theirlapping operation whereby there will be an even distribution of lappingpressure over the surface of the work piece. Uniformity of lappingpressure is a major factor in producing or causing the perfect randommovement of the work piece and eliminates the tendency for systematic orarbitrary motion on the part of the work piece.

It is an object of this invention to provide an apparatus constructedand arranged for substantially perfect free random movement of the workpiece.

It is another object of this invention to provide a support for the workpiece with relation to the lapping members for free random movement ofthe work piece.

It is a further object of this invention to provide an even distributionof lapping pressure over the surface of the work piece to avoid thepresence and effect of the pressure points of lapping as commonlydeveloped or generated by the pressure of gravity.

It is an object of this invent-ion to provide a plurality of lappingmembers constructed and arranged to have selfaligning axes.

It is also an object of this invention to provide lap membersrespectively being constructed and arranged to exercise variable thrustforce and variable rotating action in connection with a stationary orrotatable supporting member for the work piece and further to providefor a cyclical variation of said thrust force and rotative action.

These and other objects and advantages of the invention will be fullyset forth in the following description made in connection with theaccompanying drawings in which like reference characters refer tosimilar parts throughout the several views and in which:

FIG. 1 is a view in front elevation with some portions being brokenaway;

FIG. 2 is a top plan view of applicants apparatus;

FIG. 3 is a view in end elevation with some portions being broken away;

FIG. 4 is a fragmentary view of a detail of applicants apparatus inperspective on an enlarged scale;

FIG. 5 is a fragmentary view in vertical section taken on line 5-5 ofFIG. 1 as indicated by the arrows, and shown on an enlarged scale;

FIG. 6 is a view similar to FIG. 5 showing a modification thereof; and

' te States atent O "ice FIG. 7 is a fragmentary view of a modificationof a portion of applicants device in vertical section on an enlargedscale.

Referring to the drawings, applicants lapping apparatus 10 in theembodiment of the invention here disclosed comprises a principalsupporting member 1-1 here shown in the form of an upstanding shaftanchored in a supporting base 12 of suitable construction and hereindicated diagrammatically only.

Carried by said shaft 11 is a plate member or tray 14 shown to besubstantially rectangular in plan and having a somewhat rearwardlycentrally located aperture 15 having an integral depending hub portion16 forming a split clamp secured to said shaft by clamp bolts 181.

Upstanding substantially forwardly transversely of said plate member 14and adjacent either end thereof are spaced plate brackets 2.0 and 21having right-angled lower end portions secured to said plate member bybolts 22. Secured to the upper forward side portions of said members 21and 22 by bolts 24 is an elongated horizontally disposed supportingframe member 25 substantially rectangular in cross section.

With particular reference to FIG. 5, a work piece supporting structure29 is indicated comprising a bearing block .33 secured to saidsupporting member 25 by bolts 2'7 and being positioned substantiallycentrally longitudinally thereof. Said bearing block has a bore 31vertically therethrough with an annular groove 32 of some widthcentrally of the bore of said block. A transverse passage 33 connectssaid groove to the atmosphere and connected to said passage in asuitable manner is a conduit 34 which will communicate with a suitablesupply of fluid under pressure. Recessed at either end of said block 39are annular bushings 37. lournaled in said block is a shaft 39 extendingoutwardly at either end thereof and is here shown having a collar 40thereabout secured thereto by a set screw 41 and bearing on the uppersurface of said block acting as a thrust bearing or retaining ring.Disposed about said shaft adjacent either end of said groove 32 aresealing rings 42 indicated as being O-rings. As indicated, the upperportion of said shaft is shown having a bore 43 therethrough with radialpassages 44 at the lower end of said bore within the area of said groove32. Secured to the lower end of said shaft by a set screw 4-6 is apulley 48.

Carried on the upper end of said shaft 35 and secured thereto by a setscrew 56 is a supporting head 38 cylindrical in form having a reliefarea 51 at its lower side and extending upwardly thereof is anupstanding cup portion 38a of reduced diameter having its annular upperend portion 38b arcuate in transverse section and of suitable dimensionto adequately support said spherical work piece 53. Said cup portion hasa relief portion 38c centrally thereof in communication with said bore53.

A drip tray 55 having a retaining wall thereabout is here shown providedwith a central aperture 55a and is disposed over said block 30 havingfrictional supporting engagement therewith by means of an annularresilient collar or gasket 56 lining said aperture.

With reference to FIG. 3, the rearward portion of said plate member 14is shown here having an upwardly extended angled shelf portion 64 madeintegral therewith in a suitable manner. Carried on said member 14 is amotor 66 secured by bolts 67. Said motor is equipped with a drive shaft68 having secured thereto a pulley 69 having a belt 74) pass thereoverand over said pulley 43. Said motor is provided with a variable speedcontrol mechanism operated by the lever 72. Mounted on the upper shelfportion is a small timing motor 74 of a common design having anupstanding drive shaft 75 having a crank 76 secured thereto and alsoconnected to said lever 72 by a wire link 78. Hence said motor 74-operates to vary the speed of the motor 66 by reciprocating the variablespeed control lever 72 and is adapted to do so cyclically.

In cooperative association with the supporting member 29 are lappingassemblies fill and 863. The structure of each including associatedelements is the same. Hence only one lapping assembly will be describedand corresponding parts of the other will be indicated by like nu meralswith primes added. a I

Vertically supported by said member 25 is a lap supporting bracket 81secured thereto by an angled plate 82 with bolts 33 extending throughone face portion of said plate and longitudinal slots in said frame forlongitudinal adjustment with a bolt 84 extending through the other faceportion of said plate and a vertical slot 81a of said bracket. Saidbracket is substantially rectangular in cross section and is disposed ina plane at right angles to the plane of said supporting member 25. Saidbracket has a spaced pair of upwardly extending armstiilb secured bybolts 81c forming a bifurcated upper end port-ion 81d having pivotedtherein by means of bolts '85 a gimbal 86 of a common design.

The center or vertical plate 86a. of said gimbal has an aperture 88btherein through which is disposed one end of an elongated sleeve 38secured therein by set screws 96 as indicated in FIG. 4, with saidscrews also serving to provide a vertical axis for the pivotal movementof said plate 86a. Said sleeve is shown having bushings 92 at either endthereof and slidably disposed therethrough is a spindle 94 extendingoutwardly'at either end of said sleeve and in the present embodiment isshown being tubular in form having a passage 94a therethrough.

Secured to the upper or outer end of said spindle 94 by a set screw 97is a collar 1 6 having integral therewith oppositely extending pins 98from the periphery thereof. Pressed onto the lower or inner end portionof said spindle is a collar 1%. Extending outwardly of said collar andforwardly of said spindle are a plurality of projecting fingers 101having respectively disposed therethrough cocked set screws 103 whichare inclined downwardly and inwardly in the direction of said collar100, as indicated in FIGS. and 7. Constructed and arranged to beadjustably positioned between said set screws and in engagement withsaid collar 1% is a cylindrical lap tool or lap head 105 of a commondesign having a semi-spherical recess therein for lapping or polishingengagement with the work piece. Said lap head is here shown havingspaced from its forward end an annular angular notch 105a having aninclined wall or land in a plane substantially at right angles to theplane of the axis of said set screws 163. Said lap head is formed havinga central aperture or bore 105b, as

indicated in FIG. 7.

Upstanding from said sleeve 88 forward of said gimbal 86 is a platemember 110 having an integral hub or collar portion extending forwardlythereof with said collar and plate portions being apertured to slip oversaid sleeve and be secured thereon by a set screw 111. An L frame-likebalancing member 112 is secured by bolts 113 at the free end of itsshorter leg to the upper end of said plate 11% and extends rearwardlyand downwardly therefrom. At the lower free end of said member 112 areoutwardly extending pins 112a adapted to retain weights 115. Said member112 will be weighted to balance the lapping assembly 80 to locate thecenter of gravity with reference to the point of said gimbal 86 wherebythere will be no pressure'of gravity of consequence affecting theoperation of the lap head 105. V

Mounted on the forward side of said plate member 110 is a small motor117 which will be connected to a suitable source of power and which willrotate an eccentric crank 121) mounted thereon. An elongated U bracket122 is mounted on said sleeve 88 forwardly of said motor 117 havingupstanding legs apertured to have a rod 124 slidably disposedtherethrough with said rod having a yielding upstanding pin 125 with acoil spring 126 about said rod extending between said pin and therearward upstanding leg 122a of said bracket whereby said rod isnormally urged forwardly into contact with said cylindrical plate member1% to move the spindle 94 and lap head 1&5 forwardly into engagementwith the work piece 53. An arm 128 connects the upper end portion ofsaid pin 125 and said crank 1-20 to control and vary the axim thrustexerted.

Spaced rearwardly of said bracket 81 is an elongated upstandingvertically angled plate bracket 13% having an open-ended vertical slot136:: at its lower end portion through which is disposed a bolt 132adjustably securing said bracket to said member 25.

Carried at the upper end portion of said bracket 130 in a suitablemanner as by being welded thereto is a housing 132 here shown as asleeve bearing having a shaft 135 journaled therein and extendingoutwardly at either end thereof and having a passage 1% therethrough.Said shaft will be substantially in axial alignment with said spindle 9-5. Carried at the upper extended portion of said shaft 135 is a pulley140 secured thereto by a set screw 141.

Secured to the other end of said shaft 135 isa collar 149 secured as bybeing pressed onto said shaft. Disposed about said collar 149 is acollar 159 secured by a set screw'151 and having extending forwardlythereof a pair of diametrally spaced pins 152 integral with said collarand constructed and arranged to engage the pins 93 to form a pin or forktype coupling.

With reference to FIG. 3 particularly, secured to said shaft 11extending rearwardly thereof and being spaced above said tray or platemember 14 is a tray or shelf memher 160 indicated here as beingapertured to be disposed over said shaft 11 and having a depending hubportion 161 forming a split clamp which is tightened by bolts 163. Saidtray 16!) has an upwardly extending angled portion 165 similar to thesupporting portion 64. A variable speed motor of a common design whichwill be connected to a suitable source of power is secured onto saidtray 160 as by bolts 171, and is equipped with a variable speed lever173. Secured onto said shelf 165 is a small timing motor 177 similar tomotor 74 having a drive shaft 173 carrying a crank 179 connected to saidlever 173 by a crank arm or connecting link 180. Secured to the driveshaft 172 of said motor 170 is a pulley 182 and passing thereover andover said pulley 149 is an endless belt 185.

Said tray 160 extends to either side of said shaft 11 to carry motor 179in operative alignment with the lap assembly 8t} and a second identicalmotor 17b in a corresponding operative association with the lap assembly8t).

Carried upwardly of said shaft 11' is a tray having integral therewith asplit clamp 191 secured to said shaft. Supported on said tray is avessel 193 to carry a supply of suitable lapping compound which in theembodiment here shown will be gravity fed by a depending tube 195whereby said compound as indicated in FIG. 1 will drip onto the workpiece.

In operation, the work piece which in the embodiment of the inventionhere disclosed is a spherical or ball-like member 53 supported in thecup-like supporting member 38. The lapping assemblies 3% and 8%respectively will be positioned to have the lap heads 1&5 and 105'engaging the work piece at either side thereof. The lapping assemblieswill be-counter-balanced by the members 112 and 112 respectively so thatthe centers of specific gravity with reference to the gimbals as and 86so far as the lap headslhj and 165 are concerned, will be at such pointsthat no weight or pressure of any consequence caused by gravity willaffect the lapping of the work piece. This represents a substantialimprovement over the regular practice in lapping wherein the upperportion of the lap head on the upper portion of the work piece willexert greater pressure upon the work piece than will the lower portionthereof. Moreover the gimbals in providing a relatively uninhibiteduniversal pivotal support for the lap heads permit the lap heads tofreely align themselves with the surface areas they are respectivelylapping. Thus the counter-balancing and universal pivotal supportpresent here permit a uniformity of lap pressure on the work piece andthis in addition to the varied axial thrust present contributes to amore perfect random movement on the part of the work piece. Theapplicants structure serves to avoid a systematic action of lappingwhich is a common occurrence in ordinary practice and which serves toaffect the work piece to prevent it from exercising perfect randommovement.

Thus the lapping of the work piece 53 will be substantially free fromany effect of the pressure of gravity. The only substantial pressureupon the work piece will be the axial thrust exerted by the spindles 94and 94. The thrust exerted by said spindles will vary as a result of theaction of the motors 116 and 117 in governing the pressure of thesprings 126 and 126 on the shafts 12.4 and 124' in respectively causingsaid shafts to increase and decrease the axial thrust of the spindles 94and 94 cyclically in the embodiment of the invention here presented.Said spindles will be respectively rotated through associated elementsby means of the motors 170 and 17 respectively driving the pulleys 140and 14h. Said pulleys may be and normally will be respectively rotatedat different rates of speed and in the same or opposite directions asmay be desired. Preferably they will be rotated in opposite directions.As a result of the action of the timing motors 177 and 177', there willbe a cyclical variance in the rate of speed at which said pulleys arerespectively driven, and thus there will be a cyclical variance of theangular velocities of the lap heads. This will be controlled as may bedesired. The shaft 39 will be rotated through associated elements by themotor 66 and the ro tation of this shaft may be cyclically varied bymeans of the timing motor 74. The shaft 39 may be used as stationarysupport as may be desired in the lapping operation.

As illustrated in FIG. 5, the supporting cup-shaped portion 38a forms ahydrodynamic bearing with fluid being introduced through the supply line34 and the passage 43 into the relief portion 380 of said portion 38aand onto the land or edge portions 381) on which the work piece issupported. A relatively wide groove 32 in the bearing block 39 providesa chamber for the fluid and from this point it passes through thepassage in the shaft 39 upwardly to the supporting portion 38a. Theportion 38a will be of a size to suitably support the work piece.

It is noted that a pin type of coupling is used to transmit the drivingforce from the pulleys 140 and 140' respectively to the spindles 94 and94 respectively so that no adverse torque is developed to affect theaxial alignment of the spindles 94 and 94 nor to affect their delicatebalance as previously indicated. The spindles 94 and W will be alignedwith respect to one another so that an extension of their axes willintersect at a point representing the center of the work piece.

Lapping compound is indicated as being gravity fed onto the work pieceby means of the supply line 195, as indicated in FIG. 1.

Applicants device has been unusually efficient and effective in lappingspheres to a degree of perfection in sphericity which has heretoforeseemed impossible as a practical thing. It provides an unusual degree offreedom of random movement of the workpiece and the uniformity oflapping pressure not only contributes to the unusual degree of randommovement present, but also directly contributes to the perfectsphericity obtained.

With reference to FIG. 5, it is noted that the lap head N is adjustablyheld by the spaced cocked set screws 103 which allow for a very niceadjustment of said lapping head in setting up the apparatus for alapping operation.

With reference to FIG. 6, a work piece supporting structure 280 is shownwhich is a modification of the supporting structure 29. The supportingstructure 2% is 6 secured to the member 25 by bolts 27 and supports thetray 55 in like manner, as in connection with the supporting member 29.

The structure 200 is disclosed as being stationary and comprising ablock or housing 201 having a central vertical passage 202 thereinconnected at its lower end by a suitable fitting 203 to a supply line264 communicating with a suitable supply of fluid under pressure.

The upper portion of said block 261 has a vertical bore 205 therein intowhich is pressed the lower end portion of an upstanding shaft 207 havinga passage 2% therethrough in communication with the passage 2%. Carriedon said shaft is a supporting head 21% having a central bore 217extending upwardly therein into which is received the upper portion ofsaid shaft 2&7. Said member 210 has a substantially cylindrical baseportion having a relief portion 211 at the under side thereof and havingupstanding therefrom a saddle-shaped supporting portion 212 arcuate inlongitudinal vertical section with its curvature being such as to nicelyembrace the segment portion of the work piece disposed therein. Saidmember 2-16 is removiab ly held in position by a set screw 213.

The modified supporting member above described provides a stationarysupport for the work piece. It is noted that the supporting portion 212in being saddle-shaped provides support for a larger segment of the workpiece than does the supporting portion 335:, as indicated in FIG. 5.This is particularly adapted to be used as a hydrostatic bearing withfluid under suitable pressure being introduced through the passages 232and 2% to provide a fluid support for the work piece. In all respectsthe operation will be as above described.

Detail structure of the lapping assemblies 34B and till is indicated inthe sectional view shown in FIG. 7. However in addition in FIG. 7 areshown two elements not indicated in the assemblies as shown in FIG. 1and which provide an alternate operation in feeding lapping compound tothe work piece and this is in substitution for the receptacle 193 andits feed line 195.

A supply line 145 is shown connected to the extended end of the boredshaft outwardly of the pulley by a rotary seal 146. The supply line willbe connected to a suitable source of lapping compound.

The passage 136 in the shaft 135 is of a smaller diameter than thepassage in the spindle 94. A tube 155 will have one end pressed intosaid passage 136 and have its other end extend freely into the passageof said spindle to provide a line of communication from said supply linethrough the passage 94a of said spindle.

Thus with this arrangement lapping compound may be fed onto the workpiece through either spindle 94 or 94 or through both as may be desired.

Thus it is seen that I have provided a relatively simply constructedlapping apparatus which provides an unusual degree of uniformity inlapping a work piece. This apparatus has proved to be unusuallysuccessful in operation.

It will of course be understood that various changes may be made in theform, details, arrangement and pro portions of the parts, withoutdeparting from the scope of applicants invention which, generallystated, consists in a device capable of carrying out the objects aboveset forth, in the parts and combinations of parts disclosed and definedin the appended claims.

What is claimed is:

1. A lapping apparatus for lapping a spherical body having incombination, a plurality of laps, balanced means respectively supportingsaid laps for universal pivotal movement, and fiuid means verticallysupporting said spherical body in lapping engagement with said laps.

2. A lapping apparatus for lapping a spherical body having incombination, a plurality of laps, means respectively supporting saidlaps for axial and rota-tive movement, means automatically cyclicallyvarying said axial movement of said laps and means supporting saidspherical body in lapping engagement with said laps.

'7 3. A lapping apparatus for lapping a spherical body having incombination, a plurality of laps, balanced means respectively supportingsaid laps for uninhibited universal alignment'with the surface of saidspherical body, and iluid means vertically supporting said sphericalbody in lapping operation.

4. A lapping apparatus for lapping a spherical body having incombination, a plurality of laps, said laps respectively comprisingspindles, slee es respectively having said spindles disposedtherethrough for free axial and rotative movement, means universallypivotally supporting said spindles, means counter-balancing saidspindles fixing their respective centers of gravity at their pivotalsupporting points for uniform pressure of said laps about the full areaof their engagement with said spherical body,

and means vertically supporting said spherical body in lappingengagement With said laps.

5. A lapping apparatus for lapping a spherical body having incombination, a supporting structure, a pair of lap assemblies havingadjacent end portions, means in connection with said supportingstructure universally pivotally supporting said lap assemblies inopposed relation,

an upstanding member comprising a fiuid cushion sup-' heads, and meansrotating said lap heads.

6. The structure set forth in claim 5, and means rotating saidsupporting member of said spherical body and means automaticallycyclically varying the rate of said rotation.

7. A lapping apparatus for lapping a spherical body having incombination, a supporting structure, a lap assembly comprising a laphead, rneans mounting said lap assembly on said supporting structure foruniversal pivotal movement, means pivotally counterbalancing said lapassembly with respect to the point of said mounting means to negativethe eilect of gravity at the point of said lap head in operatingposition.

8. The structure set forth in claim 7, said lap head having axialmovement, and means for automatically cyolically varying the axialthrust of said lap head relative to said spherical body.

9.' A lapping apparatus for lapping a work piece having a sphericalsurface having in combination, a. plurality of laps, balanced meansrespectively supporting said laps for axial and rotative movement, andmeans respectively supporting said last mentioned means for freeuniversal alignment of said laps to said spherical surface.

10. The structure set forth in claim 9, means automatically cyclicallyvarying said axial and rotative movement.

11. The structure set forth in claim 9, said last mentioned means beingremote from said laps.

12. The structure set forth in claim 9, and means comprising a iluidcushion supporting said Work piece in lap ping engagement with saidlaps.

References Cited in the file of this patent UNITED STATES PATENTS'1,806,918 Riggs May 26, 1931 1,950,785 Capps Mar. 13, 1934 2,405,344Cloutier Aug. 6, 1946 2,479,898 Beaude-tte Aug. 23, 1949 2,787,093S-undberg Apr. 2, 1957 2,892,326 Porter June 30, 1959 3,024,578 MushkinMar, 13, 1962

1. A LAPPING APPARATUS FOR LAPPING A SPHERICAL BODY HAVING INCOMBINATION, A PLURALITY OF LAPS, BALANCED MEANS RESPECTIVELY SUPPORTINGSAID LAPS FOR UNIVERSAL PIVOTAL MOVEMENT, AND FLUID MEANS VERTICALLYSUPPORTING SAID SPHERICAL BODY IN LAPPING ENGAGEMENT WITH SAID LAPS.